New technologies of waterproofing in residential buildings
In spite of many fold advancement made in concrete technology and ability to produce high quality concrete, it has not been possible to really make waterproof structures. The problem of waterproofing of roofs, walls, bathrooms, toilets, kitchens, basements, swimming pools and water tanks etc. have not been much reduced. There are number of materials and methods available in the country for waterproofing purposes. But most of them fail due to one or the other reasons. Waterproofing has remained as an unsolved complex problem. A successful waterproofing not only depends upon the quality and durability of material but also the workmanship, environment and type of structures.
The first real need for waterproofing dates back to the days of Noahs Ark. The 40 days of incessant rain inspired people to take some course of action to prevent water from entering their habitat. In the early days people relied upon thatch, such as straw, reed, leaves and other dried vegetable matter as a barrier against water entering their home. Over time more sophisticated waterproofing materials were adopted. These included: animal skins, timber shingles, and natural stones like slate. The architectural designs of the day such as high pitched roofs helped overcome some of the shortfalls and limitations of the materials that were used. Over the centuries other waterproofing materials were used such as metals e.g. copper, lead, zinc, and tin.
Waterproofing has come a long way since Noah’s day. The discovery of oil, coupled with the advances of chemistry saw the arrival of numerous petroleum derived waterproofing products such as bituminous, butyl rubber, neoprene rubber, hypalon etc.
Technological improvements and breakthroughs are occurring on a daily basis. Over time today’s waterproofing membranes such as polyurethanes, acrylics and polyesters will become as antiquated as leaves and animal skins are today.
Waterproofing is a method by which an item is made resistant to damage by water. Waterproofing is the formation of an impervious barrier which is designed to prevent water entering or escaping from various sections of building structures. Internal areas that are waterproofed include bathrooms, shower recesses, laundries and toilets. Whilst an external area waterproofed extends to roofs, planter boxes, podiums, balconies, retaining walls and swimming pools.
BENEFITS OF WATERPROOFING
- Increased property value
- Structurally sound foundation
- A healthier home environment for a family
- A warmer basement during winter
- Enjoy an increased living space
- A more attractive and more comfortable home
THE CASUALTIES OF WATER DAMAGE INCLUDE
- Rotting of timber structures and finishes such as floor joints, beams, floors, studs, skirting, architraves and frames.
- Corrosion of metals such as steel reinforcement in concrete, steel beams, lintels, metal door frames etc.
- Swelling of plasterboards and the subsequent debonding of ceramic tiles.
- Electrical hazards causing the possible short circuit of lighting and power points.
- The blistering of paint.
- Unsightly deterioration of the building facade.
- Health problems due to dampness, which may lead to respiratory problems.
- Rotting carpet.
- The importance of waterproofing can not be overstated. The damage caused to the building’s structure, coupled with the high cost of rectification warrants the careful design and application of waterproofing.
- The role of waterproofing is to protect a building’s visual and structural integrity. It achieves this by forming an impervious membrane that prevents water entering or escaping from wet areas to dry areas.
- In order to effectively fulfil this role a membrane must possess the following qualities:
- The membrane must be impermeable to prevent the passage of water.
- Flexibility – membranes need to accommodate any normal movement that may occur in building structures.
- The membrane must be durable, it must be able to retain it’s integrity over a long period of time.
- The membrane must lend itself to design details in a building. It must be suitable for each specific application. The membrane is useless if it cannot be applied where needed because of structural details.
- The membrane must be able to breathe permitting the escape of moisture vapours from building interior and substrates.
- The membrane must be compatible with adhesives to ensure long term adhesion where tiles are directly fixed over the membrane.
- User friendly, the membrane must be easy to apply, relatively lightweight, non hazardous, and environmentally safe.
- In exposed areas such as rooftops, the membrane should require little maintenance, and in the event of damage must be easily repairable.
- It should provide a continuous film, without areas of weakness such as overlaps, which could prove to be a potential source of water entry.
- The membrane must be suitable to withstand environmental and climatic conditions.
TYPES OF WATERPROOFING
There are generally two types of waterproofing membranes – sheet membranes and liquid membranes. The nature of the problem to be addressed determines which type of membrane to be used.
- Sheet Membranes
The purpose of sheeting membrane is to completely cover any imperfections in the substrate or background. They are numerous and include:
Metal sheets in the form of lead, copper or stainless steel flashing or trays.
Multilayer bituminous paper system with gravel topping for protection.
Butyl rubber sheeting
Semi-rigid asbestos asphalt sheeting
E.P.D.M. Ethylene propylene Diene Monomer
Chlorosulphanated rubber (Hypalon)
Torch-on sheeting consists of layers of polypropylene bitumen modified.
The sheeting membranes can be applied as fully bonded to the substrate or unbonded. In both cases sheets must be overlapped about 100mm wide and bonded to each other by adhesive or by heat welding. The seams are the weakest point in the system.
Sheeting membranes in general suffer from poor exposure resistance, temperature stability and little recovery from deformation.
All sheet membranes require venting if the substrate is water logged, or severe bubbling will occur developing stresses onto the adhesive leading to eventual adhesion fracture.
The advantages of sheeting membranes provide highly trafficable surfaces and have insulating properties.
- Liquid membranes
The liquid applied membrane provides a fully bonded, continuous seam-free, homogenous layer with no laps or joins which is a major advantage over sheeting membranes.
Some of the liquid membranes available are:
- Mastic asphalt
- Two components polyurethane tar modified
- Two components tar epoxies modified
- Single pack moisture curing polyurethane
- Water based epoxy two part for hydrostatic pressure situations
- Polyester resin two parts reinforced wit fibreglass matt
- Flexible epoxy resin two parts
- Bitumen latex modified single pack
- Acrylic co-polymer water based single part
- Acrylic co-polymer cement modified two components
In general liquid applied membranes are easy to apply, seamless, semi-flexible or elastrometric, ease of detailing, ease of maintenance and repair, UV resistant and economical. One of the important characteristics of liquid membranes is its ability to breathe. Regardless of which class of membrane is used, waterproofing membranes are only as good as the applicator. Manufacturers and distributors expect their product to be applied as specified. Failure to adhere to their recommendations can retard the performance of the membranes.
VARIOUS WATERPROOFING MATERIALS
It should be remembered that the use of plasticizers, superplasticizers, air-entraining agents, pozolanic materials and other workability agents, help in reducing the permeability of concrete by reducing the requirement of mixing water and hence they can also be regarded as waterproofing materials. In addition, there are other materials and chemicals available for waterproofing concrete structures.
These materials can be grouped as follows:-
- Integral Waterproofing Compounds
- Acrylic Based Polymer Coating
- Mineral Based Polymer Modified Coatings
- Chemical DPC for Rising Dampness
- Waterproofing Adhesive for Tiles, Marble and Granite
- Silicon based Water Repellent Material
- Injection grout for cracks
- Protective and Decorative Coatings
- Joint Sealants
Using brush on waterproof compounds can be an easy and effective way to damp proof or fully waterproof your foundation. These compounds can also be used to give your wall a unique texture! Many of these products claim to be waterproof when they actually are not. For this reason it is better to read carefully the literature that comes with waterproof compound.
When using waterproofing compounds, the best results are achieved when the compound is applied to the positive side of the wall. The positive side of the wall is the side of the wall where the water is entering, not coming out. With basement foundations, you will most likely be required to do some digging in order to get to the positive side of the foundation walls.
The application process is another important consideration. First of all, the walls must be clean before applying the compound. All paint must be removed as well. Consider sandblasting the surface or using a pressure washer to remove all dirt and paint. Once the walls are clear, they must be wet down before you apply the compounds. Keep in mind; two coats of thin paint work better than one thick coat. Popular manufacturers of brush on waterproofing compounds include ChemMasters, Chemrex, Master Builders, and Quikrete.
Once the waterproofing product has been applied, it is sure to do a fantastic job of stopping water from entering. You must be sure to follow the instructions for each product though. Improper application can lead to ineffective waterproofing. Keep in mind that these products can also be used to texture walls. They come in a grey and a pure white colour and the texture is sandy. Decorative swirls can be made on your walls if you use a stiff brush with a handle.
The one drawback to using brush on waterproof compounds is the fact that they are not elastic. Basically, they do not stretch and this makes it impossible for them to waterproof a foundation that develops cracks or gaps. If you know that your foundation has been forming continuous cracks, you will need to stabilize your wall, use the epoxies, and then coat the wall.
INTEGRAL WATERPROOFING COMPOUNDS
The integral waterproofing compounds have been in the use from the last 4 – 5 decades. They were used as admixtures to make concrete waterproof. These conventional waterproofing admixtures are either pore fillers, or workability agents or water repellents, and as such they are useful to a limited extent. In situations where concrete is continuously in wet or in damp condition, integral water proofing will be of some use. The classical integral waterproofing compounds are Cico, Pudlo, Impermo, Accoproof etc.
There are new brands of integral waterproofing compounds such as Mc-special DM, Dichtament DM, Putz-Dichtament from MC Bauchemie and conplast proplapin 421 IC, conplast prolapin I-P etc. from Fosroc chemicals are useful in making concrete more workable and homogenous. They also help in reducing the w/c ratio, which properties extent better waterproofing quality. The modern waterproofing compounds are a shade better than the old products. The performance requirements of integral waterproofing compounds are covered in IS2645 of 1975.
ACRYLIC BASED POLYMER COATINGS
Structural inadequacy, or failure to adhere to the proper detailing of reinforcement, or the unequal settlement, variation in temperature and long term drying shrinkage with age etc are some of the additional reasons for development of cracks in concrete members.
In such situations a membrane forming waterproofing materials are ideal. The membrane should be tough, water resistant, solar reflective, elastics, elastomeric and durable. They allow the movement of the concrete members, but keep the qualities of the membrane intact.
One such material available today is Roofex 2000, material manufactured by MC-bauchemie Pvt. Ltd. The surface is cleaned; a priming coat and dust binder is applied over which the Roofex 2000 is applied by means of brush or spray in two coats, right angles to each other. In applying this material manufacturers instructions should be strictly followed.
Any cracks in the plaster of parapet wall or vertical surface can be treated with this material. Generally this material is available in white colour but it can be made to order in any other colour aesthetic requirements.
The Indian Standard is being formulated for the use of such membrane forming waterproofing coatings.
MINERAL BASED POLYMER MODIFIED COATINGS
Waterproofing of concrete, brick masonry and cement bound surfaces can be achieved by a specially made slurry coatings. Slurry consists of specially processed hydraulically setting powder component and a liquid polymer component. These two material when mixed in a specified manner forms a brushable slurry. Two coats of this slurry when applied on root surface or on any other vertical surface in basement, water tank or sunken portion of bathroom etc. forms a long lasting waterproofing coat. This coating requires curing for a week or so. The coating so formed is elastic and abrasion resistant to some extent. To make it long lasting, the coating may be protected by mortar screeding or tiles. The trade name of the above material is Dichtament DS, manufactured by MC- Bauchemie Pvt. Ltd. The brush bond of Fosroc coy and another material called xypex are also available in the market.
The materials described above although exhibit good waterproofing qualities the coating is not very elastic. Its performance in sunken portion of bathroom and such other areas where the concrete is not subjected variation in temperature will be good. But it may not perform well on roof slab for not being flexible to the require extent, to cope up with the thermal movement of roof slab.
There is a modified version of Dichtament DS called Dichtament DS-flex. It is formulated in such a way that higher amount of polymer component is added to make it to take care of possible small cracks in roof slab or such other situations.
A further modified version of the above has been made to give a better waterproofing and abrasion resistance to the treatment. The modified version will make the coating tough, more elastic and better waterproofing. This modified version of waterproofing system is specially applicable to terrace gardens, parking places, basements, swimming pools, sanitary areas etc. this coating also gives protection to chlorides, sulphates and carbonation attack on bridges and also protect underground structures. The trade name is Zentrifix Elastic, manufactured by MC-Bauchemie (India) Pvt. Ltd.
The above is one of the best waterproofing treatments when application is done strictly as per manufacturer’s instructions. Being flexible and having good crack bridging quality, it is an ideal material for prefabricated roof construction. Before applying the surface should be made damp but not wet. It can be applied by trowel or brush in two coats. A gap of about 3-4 hours is given between successive coats. Though a standard thickness of 2-3 mm are achieved in two coats, in exceptional situation a maximum thickness of 4 mm could be allowed and in such a case the application should be done in three coats. A three coat treatment could be given to the external face of masonry wall in basement construction.
For the mineral based polymer modified coatings the BIS specifications is under preparations.
PROTECTIVE AND DECORATIVE COATINGS
RCC members such as sunbreakers, louvers, facia, facades, sun shades and chajjas, crack and spall off within a matter of a few years, particularly when the cover provided to these thin and delicate members are inadequate. Water seeps into these members and corrodes the reinforcement in no time. Corrosion is also accelerated by carbonation. To enhance the durability of such thin member is to make them waterproof, carbonation resistant coating is given. Incidentally it will present a aesthetic and decorative look. A number of such protective, waterproof decorative paints, based on acrylic polymer and selected mineral filler are available in market. Emcecolour-Flex is one such paint manufactured by MC Bauchemie and Dekgaurd S is the product of Fosroc chemicals. Generally they are white but could be produced in any colour in the factory.
Often old buildings are not provided with damp-proof course. The water from the ground rises by capillary action. This rising water brings with the dissolved salts and chemicals which result in peeling of plaster affecting the durability of structure, and also make building unhygienic. Now we have materials that can be injected into the wall at appropriate level to seal the capillaries and thereby to stop the upward movement of the water. The system involves a two component material called samafit Vk1 and samafit Vk2 manufactured by MC Bauchemie Pvt. Ltd. Above the ground level and below the plinth level, holes are drilled in a particular system.Samafit VK1 is injected into the hole till absorption stops. After another ½ to 1 hours time the othe fluid namely Samafit VK2 is similarly introduced. These two liquid react with each other to form a jelly like substance which block the capillary cavities in the brickwall and stop the capillary rise of water. In this way rising dampness in buildings, where damp proof course is not provided earlier, can be stopped.
WATERPROOFING ADHESIVES FOR TILES, MARBLE AND GRANITE
The normal practice followed for fixing glazed tiles in bathroom, lavatory, kitchen and other places is the use stiff neat cement paste. The existing practice, though somewhat satisfactory in the indoor conditions from the point of fixity, such practice is unsatisfactory when used in outdoor conditions and also from the point of view of waterproofing quality. The cement paste applied at the back of tiles do not often flow towards the edges of the tiles and as such water enter at the edges, particularly when white cement applied as joint filler become ineffective. In large number of cases it is seen that paintings and plasters get affected behind these glazed tiles supposedly applied to prevent moisture movement from wet areas.
Cement paste is not the right material for fixing the glazed tiles. There is polymer based, hydraulically setting, ready to use, waterproof tile adhesive available in the market. They offer many advantages over the conventional method of tile fixing such as better bond and adhesion, strengths, faster work, good waterproofing quality to the wall. They are also suitable for exterior and overhead surfaces. No curing of tile surface becomes necessary. If the wall and plastered surface is done to good plumb, a screeding of only 1 – 2 mm thickness of this modern material will be sufficient to fix the tiles in which case, the adoption of this material will also become economical. The modern tile adhesive material offers special advantages for mixing glazed in swimming pools both on floor and at side walls. It provides one more barrier for the purpose of waterproofing.
Many a time, the glazed tiles fixed on the kitchen platform or bathroom floor gets dirty or damaged. It requires to be replaced. Normal practice is to chip off the old tile, screed cement paste or mortar and then lay the new tiles. With modern tile adhesive, it is not necessary to remove the old tile. The adhesive can be screeded on the existing tiles and new tiles are laid over the old tiles. The bonding quality is such that good adherence takes place tile over tile. This saves considerable cost and time and operation becomes simple.
Marble and granite are increasingly used for cladding wall surfaces both internally and externally. Marble and granite have become the most common treatment for external cladding of prestigious buildings. They are used in the form of tiles or large panels. In the past for fixing thin marble and granite tiles cement paste was used for fixing large slabs and panels, epoxy and dowel pins were used. Now there are specially made ready to use high strength polymer bonding materials available, which can be used with confidence both for internal and external use. Requirement of dowel are eliminated in most of the cases except for cladding of large panels at very high level for extra safety. Marble and granite can even be fixed on boards, inclined surface, underside of beams and in ceilings by the use of this new powerful adhesives.
Zentrival PL for fixing glazed tiles and ceramic tiles and Zentrival HS for marble, granite and stones are the materials manufactured by MC-Bauchemie (India) Pvt. Ltd., Nitobond EP, Nitobond PVA, Nitotile SP are some of the products manufactured by Fosroc.
SILICON BASED WATER REPELLENT MATERIALS
Sometimes, in buildings, brick works are not plastered. Bricks are exposed as they are. If good quality, well-burnt bricks are not used in such constructions, the absorptive bricks permit the movement of moisture inside. Old heritage buildings built in stone masonry may suffer from minute cracks in mortar joints or plastered surface may develop craziness. In such situations one cannot use any other waterproofing treatment, which will spoil the intended architectural beauty of the structures. One will have to go for transparent waterproofing treatment. For this purpose silicon based water repellent materials are used by spraying or brushing. This silicon-based material forms a thin water repellent transparent film on the surface. The manufacturers slightly modify this material to make it little flexible to accommodate minor building movements due to thermal effect.
The application must be done in one liberal coat so that all the cracks and crevices are effectively sealed. Brick surface absorbs this material making the surface water repellent. Sometimes bricks or blocks are immersed in such materials before using for greater water repellent qualities.
These types of waterproofing materials are used in many monumental stone buildings and old places so that original look of the stone masonry is maintained, while making the masonry waterproof.
The treatment though effective, is not found to be long lasting on account of the movement of building components and the lack of required flexibility of the film. The treatment may have to be repeated at closer intervals, say once in 3 – 4 years. As it is not a costlier material, one can afford to repeat the treatment.
The material is covered in IS 12027 of 1987. NISIWA SH is the brand name of one such material manufactured by MC-Bauchemie (Ind.) Pvt. Ltd.
INJECTION GROUT FOR CRACKS
Injection grouting is one of the powerful methods commonly adopted for stopping the leakages in dames, basements, swimming pools, construction joints and even in the leaking roofs. A few years back, cement was used for grouting purposes. Cement is not a ideal material for grouting, as it shrinks while setting and hardening. Non-shrink or expansive cementing is the appropriate material. We have quite a few materials available in the market for filling up cracks and crevices in concrete structures to make them waterproof or for repair and rehabilitation of structures. The grouts are produced with selected water repellent, silicifying chemical compounds and inert fillers to achieve varied characteristics like water impermeability, non-shrinkage, free flowability etc. They are suitable for gravity grouting as well as pressure grouting. Grouting of concrete structure is one of unhealthy structures. Centicrete is the trade name of one of the materials manufactured by MC- Bauchemie. Connbex 100 is the material marketed by Fosroc chemicals.
Joints in buildings, bridges, roads and airfield pavements are inescapable. They may be expansion joints, construction joints or dummy joints. Such joints must be effectively sealed to facilitate movement of structure, to provide waterproofing quality or to improve the riding qualities. While providing large openings and windows in buildings there exists gap between wall and window frames, through which water flows inside. Such gap in window should be effectively sealed. The gaps resulting in installation of sanitary appliances are also required to be sealed. Now we have modern materials like polysulphide sealants and gun applied Silicone Rubber sealants, sanitary sealant and Acrylic sealants. Nitoseal, 215 of fosroc, Sikalastic, Sika-SII A, Sikacryl GP of Sika Qiualcrete and sani seal of Roff are some of the materials available for sealing the joints.
WATER PROOFING MATERIAL –“ASPHALT CEMENT”
Asphalt is a heavy, dark brown to black mineral substance, one of several mixtures of hydrocarbons called bitumen. Asphalt is a strong, versatile weather and chemical-resistant binding material, which adapts itself to a variety of uses. Asphalt binds crushed stone and gravel (commonly known as aggregate) into firm, tough surfaces for roads, streets, and airport runways. Asphalt, also known as mineral pitch, is obtained from either natural deposit such as native asphalt or brea or as a byproduct of the petroleum industry (petroleum asphalt). Prehistoric animal skeletons have been preserved completely intact in natural asphalt deposits, one of the most famous being the La Brea Tar Pits in Los Angeles, Califomia.
Asphalt is one of the world’s oldest engineering materials, having been used since the beginning of civilization. Around 6000 B.C. the Sumerians had a thriving shipbuilding industry that produced and used asphalt for caulking and waterproofing. As early as 2600 B.C. the Egyptians were using asphalt as a waterproofing material and also to impregnate the wrappings of mummies as a preservative. Ancient civilizations widely used asphalt as a mortar for building and paving blocks used in temples, irrigation systems, reservoirs, and highways. The asphalts used by early civilizations occurred naturally and were found in geologic strata as either soft, workable mortars or as hard, brittle black veins of rock formations (also known as asphaltic coal). Natural asphalts formed when crude petroleum oils worked their way up through cracks and fissures to the earth’s surface. The action of the sun and wind drove off the lighter oils and gases, leaving a black residue. Natural asphalts were extensively used until the early 1900s. The discovery of refining asphalt from crude petroleum and the increasing popularity of the automobile served to greatly expand the asphalt industry. Modern petroleum asphalt has the same durable qualities as naturally occurring asphalt, with the added advantage of being refined to a uniform condition free from organic and mineral impurities.
Most of the petroleum asphalt produced today is used for highway surfacing. Asphalt paving material is a dull black mixture of asphalt cement, sand, and crushed rock. After being heated, it is dumped out steaming hot onto the roadbed, raked level, and then compacted by a heavy steamroller. Asphalt is also used for expansion joints and patches on concrete roads. Airport runways, tennis courts, playgrounds, and floors in buildings all use asphalt as well. Light forms of petroleum asphalt called road oils are sprayed on roadways to settle dust and bind gravel. Another major use of asphalt is in asphalt shingles and roll roofing, which usually consists of felt saturated with asphalt. The asphalt helps to preserve and waterproof the roofing material. Other applications for asphalt include the following: waterproofing tunnels, bridges, dams and reservoirs; rustproofing and soundproofing metal pipes and automotive under-bodies; and soundproofing walls and ceilings.
The raw material used in modern asphalt manufacturing is petroleum, which is a naturally
occurring liquid bitumen. Asphalt is a natural constituent of petroleum, and there are crude oils which are almost entirely asphalt. Oil wells supply the crude petroleum to the oil refineries, where it is separated into its various components or fractions.
THE MANUFACTURING PROCESS
Crude petroleum is separated into its various fractions through a distillation process at the oil refinery. After separation, these fractions are further refined into other products which include asphalt, paraffin, gasoline, naphtha, lubricating oil, kerosene, and diesel oil. Since asphalt is the base or heavy constituent of crude petroleum, it does not evaporate or boil off during the distillation process. Asphalt is essentially the heavy residue of the oil refining process.
DISTILLING THE CRUDE
The refining process starts by piping the crude petroleum from a storage tank into a heat exchanger or tube heater where its temperature is rapidly raised for initial distillation. It then enters an atmospheric distillation tower where the lighter and more volatile components, or fractions, vaporize and are drawn off through a series of condensers and coolers. It is then separated for further refining into gasoline (considered a “light” distillate), kerosene (considered a “medium” distillate), diesel oil (considered a “heavy” distillate), and many other useful petroleum products.
The heavy residue from this atmospheric distillation process is commonly called topped crude. This topped crude may be used for fuel oil or further processed into other products such as asphalt. Vacuum distillation may remove enough high boiling fractions to yield what is called a “straight run” asphalt. However, if the topped crude contains enough low volatile components which cannot be economically removed through distillation, solvent extraction—also known as solvent deasphalting—may be required to produce asphalt cement of the desired consistency.
Asphalt may next be blended or “cut back” with a volatile substance, resulting in a product that is soft and workable at a lower temperature than pure asphalt cement. When the cutback asphalt is used for paving or construction, the volatile element evaporates when exposed to air or heat, leaving the hard asphalt cement. The relative speed of evaporation or volatility of the cutting agent determines whether cutback asphalt is classified as slow, medium, or rapid curing. Heated asphalt cement is mixed with residual asphaltic oil from the earlier distillation process for slow-curing asphalt, with kerosene for medium curing, and with gasoline or naphtha for the rapid-curing asphalt.
The asphalt cement may also be emulsified to produce a liquid that can be easily pumped through pipes, mixed with aggregate, or sprayed through nozzles. To emulsify, the asphalt cement is ground into globules 5 to 10 microns and smaller (one micron is equal to one millionth of a meter). This is mixed with water. An emulsifying agent is added, which reduces the tendency of the asphalt and water to separate. The emulsifying agent may be colloidal clay, soluble or insoluble silicates, soap, or sulphonated vegetable oils.
Asphalt may also be pulverized to produce powdered asphalt. The asphalt is crushed and passed through a series of fine mesh sieves to ensure uniform size of the granules. Powered asphalt can be mixed with road oil and aggregate for pavement construction. The heat and pressure in the road slowly amalgamates the powder with the aggregate and binding oil, and the substance hardens to a consistency similar to regular asphalt cement.
If the asphalt is to be used for a purpose other than paving, such as roofing, pipe coating, or as an undersealant or water-proofing material, the asphalt may be oxidized, or air blown. This process produces a material that softens at a higher temperature than paving asphalts. It may be air blown at the refinery, at an asphalt processing plant, or at a roofing material plant. The asphalt is heated to 500°F (260°C). Then air is bubbled through it for one to 4.5 hours. When cooled, the asphalt remains liquid.
ASPHALT PAVING MIXTURES
Since asphalt cement is a major constituent used in road paving, the following is a brief
There are two types of asphalt mixes: hot-mix and cold-mix. Hot-mix asphalt (HMA) is commonly used for heavier traffic areas while cold-mix asphalt is used for secondary roads.
Description of how asphalt-paving mixtures are produced. Asphalt paving mixes made with asphalt cement are usually prepared at an asphalt mixing facility. There are two types of asphalt mixes: hot-mix and cold-mix. Hot-mix asphalt (HMA) is more commonly used while cold-mix asphalt (generally mixes made with emulsified or cut-back asphalts) is usually used for light to medium traffic secondary roads, or for remote locations or maintenance use. Hot-mix asphalts are a mixture of suitable aggregate coated with asphalt cement. The term “hot-mix” comes from the process of heating the aggregate and asphalt before mixing to remove moisture from the aggregate and to obtain sufficient fluidity of the asphalt cement for proper mixing and work-ability.
Asphalt cement and aggregate are combined in a mixing facility where they are heated, proportioned, and mixed to produce the desired paving mixture. Hot-mix facilities may be permanently located (also called “stationary” facilities), or it may be portable and moved from job to job. Hot-mix facilities may be classified as either a batch facility or a drum-mix facility, both can be either stationary or portable. Batch-type hot-mixing facilities use different size fractions of hot aggregate, which are drawn in proportional amounts from storage bins to make up one batch for mixing. The combination of aggregates is dumped into a mixing chamber called a pugmill. The asphalt, which has also been weighed, is then thoroughly mixed with the aggregate in the pugmill. After mixing, the material is then emptied from the pugmill into trucks, storage silos, or surge bins. The drum-mixing process heats and blends the aggregate with asphalt all at the same time in the drum mixer.
When the mixing is complete, the hot-mix is then transported to the paving site and spread in a partially compacted layer to a uniform, even surface with a paving machine. While still hot, the paving mixture is further compacted by heavy rolling machines to produce a smooth pavement surface.
THE SYSTEMS OF WATERPROOFING
DRAIN TILE SYSTEMS
In the past, drainage systems were not very efficient. Also, the installation methods used to install the drainage system were inadequate and lead to bigger problems. Builders that allow them to install foundation drainage systems, which will work perfectly for many years, are now using newer products and installation methods. Furthermore, new drainage systems can provide you with tremendous peace of mind.
What builders are now coming to realize about drainage systems is that drainpipes can serve two purposes! They were originally designed to collect water and pipe it to another location where it can be transported away from the foundation. However, it is now being realized that drain pipes can also be used as a water injection system. Before installing your drain tiles, consider the benefits of giving it a dual purpose.
Both homes with shallow foundations and those with deeper foundations can have drain tiles installed next to the footers to be used as water injection systems in times of drought. The truth is that many homes are built on clay soils. In times of extended drought some clay soils can shrink so much that the foundation and footer can fall. But if your builder were to extend several vertical pipes up from the drain tile system, they could be used to add water to the clay, which would fluff the clay soils up.
In order for such a system to work effectively, it would need to be installed with care. It is recommended that the piping rest against the footer as opposed to resting on top of the footer. Also, if your builder uses plastic drain tile that has holes punched in it, the holes should point down not up. Smaller pieces of gravel can clog the holes if they are placed pointing up. Furthermore, it is very hard for the water to get into and out of the pipe if the holes are placed up.
During installation, try to install the drain tile piping fairly level. Some people assume that if there is no slope, the water will not drain. However, it will still drain water just fine if level because it will be acting as a conduit for water movement. Basically you should rest assured because the water trying to get away from the foundation will flow out of the pipe or towards a basement sump pit with little effort. Keep in mind, it especially important that you install the piping level if you are planning to use it as a water injection system because it will help the water travel fast to all parts of the system.
STORM WATER DRAINAGE
Proper storm water drainage is essential to a home’s foundation. Unfortunately, many building codes do not mandate that roof water be piped away from the foundation. Also, you have to keep in mind that building codes differ in many parts of the nation. It would be nice to have one national building code for everyone to follow, but the truth is that local building officials would end up changing the code to match local practices.
Over the past 15 years or so, urban and suburban flooding has become a major issue. One major reason why flooding has become such an issue is because storm water systems were designed many years ago without the anticipation of shopping malls or a subdivision with hundreds of homes being built. The design was simply underestimated. Today’s planners and engineers put special attention toward water retention systems.
Do you know where your roof water gets piped to? Nowadays, roof downspout water can be piped directly to underground storm water retention basins. In fact, certain designs allow the water to flow into open retention or detention features. The idea is to create a community of homes in which they all work together to prevent serious floods from developing. Even small problems can be prevented from such designs. Bottom line, the water from your roof needs to be captured and redirected to a place where it does not cause a problem.
Some communities require that storm water be piped to a central location. This is actually a very beneficial thing for your property and the property of your neighbours. I would, however, recommend making sure that the piping on your lot is durable enough to contain the water and prevent tree roots from entering the pipe. Four inch diameter plastic sewer line pipe is recommended. It’s definitely worth your time to check that the right type pipe is being used and it is installed the correct way.
INSTALLING STORM WATER DRAINAGE SYSTEM
During the installation of your storm water drainage system, you should avoid using 90 degree fittings on your piping. Of course you will need to use this type of fitting where the pipe terminates against the foundation wall and turns up to capture the roof downspout pipe. But using 90 degree fittings in others areas can cause serious problems because it creates tight bends. There may be a time when you need to have a plumber or drain cleaning company come out and unclog your pipes and these 90 degree angels will work against them. A 90 degree bend may prevent a company from extending a metal drain cleaning wire down the piping system. Considering using two 45 degree fittings glued together instead.
In addition to the type of piping used, the soil in which it is buried is also important. Avoid burying your piping in the un-compacted fill dirt alongside your foundation. The soil there will settle over time and as it settles it can seriously damage the piping. In fact, the piping can fracture or develop a negative pitch which could ruin the effectiveness of the entire system. If your pitch is off, the water can start flowing in the wrong direction.
The best place to bury the piping is in the undisturbed soil that you will typically find about 4to 5 feet away from your foundation. The piping will have to cross the uncompacted soil in order to get to the undisturbed soil, but when doing so it is best to give the piping a good pitch for extra safety. As it crosses this danger zone, give it one inch of fall for every two feet of run. Once the pipe is in the virgin soil, it can have a pitch of 1/8 to 1/4 inch of fall per linear foot of run.
Lastly, if you are present during the installation of your storm water drainage system, try to take pictures of the piping. It will come in handy in the future if you ever have to locate the piping in order to dig a hole or excavate. Having such facts on your house is a very useful thing. Be sure to place the photos and negatives in a safe place. Many homeowners find the electric box to be a very safe place because it is hardly used. However, fireproof safe boxes also work great.
Building a home requires some very careful considerations. One very important consideration involves waterproofing your foundation. Many homeowners are under the assumption that their foundation has indeed been waterproofed when in fact it has only been damproofed. There is a big difference between these two techniques. Damproofing may prevent a certain amount of water vapour from transferring into your basement, but in order to effectively protect your basement from water infiltration it must be properly waterproofed.
In the past, builders paid little attention to waterproofing foundations. Years ago builders did not even bother to apply a tar coating and they also did not have access to large sheets of plastic to retard the transfer of water vapor. This is why the basement of older homes typically has a dank moldy smell to it. Mold grows happily in environments fueled by the constant stream of moisture. In a basement, the moisture comes in through the water being carried in the soil surrounding the foundation. It enters the house through both the unprotected walls and through the concrete slab you walk across.
Waterproofing is the only way to permanently stop water and water vapor from entering your foundations walls. There are several different techniques used to accomplish this. Spray-on systems seem to work well when it comes to sealing off the pores of your concrete walls. Whatever you do, make sure you are waterproofing your foundations and not damproofing it. Damproofing is the cheap way out. It is cheap because it cost less and it is cheap because it fails to waterproof effectively. Damproofing typically consists of hot liquid asphalt sprayed on the concrete.
Many local building codes state that unfinished basements must be at least damproofed. The problem with spraying hot liquid asphalt on your concrete is that it will not ensure that your basement will remain dry. If the concrete cracks, which is often does as your foundation settles, water will once again be able to enter into your home because the hot asphalt will no longer be sealing the gap. Waterproofing may be a little more expensive, but it will keep these gaps sealed and keep your basement as dry as possible. This is very important, especially if you are planning to finish your basement in the near future.
As I mentioned earlier, there are several ways to waterproof your foundation. One way that is commonly used by homeowners involves applying a mixture of hot asphalt and rubber. A coating of one eighth of an inch is applied to the foundation and then an insulation panel is placed over the coating. The insulating panel serves as protection to the coating, as well as an insulator. Furthermore, the rubber in the mixture gives it a unique elastic quality that helps it fill cracks in the concrete, should they develop over time. Keep in mind, as mentioned earlier, damproofing compounds can’t do this.
The quality of asphalt cement is affected by the inherent properties of the petroleum crude oil from which it was produced. Different oil fields and areas produce crude oils with very different characteristics. The refining method also affects the quality of the asphalt cement. For engineering and construction purposes, there are three important factors to consider: consistency, also called the viscosity or the degree of fluidity of asphalt at a particular temperature, purity, and safety.
The consistency or viscosity of asphalt cement varies with temperature, and asphalt is graded based on ranges of consistency at a standard temperature. Careless temperature and mixing control can cause more hardening damage to asphalt cement than many years of service on a roadway. A standardized viscosity or penetration test is commonly specified to measure paving asphalt consistency. Air-blown asphalts typically use a softening point test.
Purity of asphalt cement can be easily tested since it is composed almost entirely of bitumen, which is soluble in carbon disulfide. Refined asphalts are usually more than 99.5% soluble in carbon disulfide and any impurities that remain are inert. Because of the hazardous flammable nature of carbon disulfide, trichloroethylene (TCE), which is also an excellent solvent for asphalt cement, is used in the solubility purity tests.
Asphalt cement must be free of water or moisture as it leaves the refinery. However, transports loading the asphalt may have moisture present in their tanks. This can cause the asphalt to foam when it is heated above 212°F (100°C), which is a safety hazard. Specifications usually require that asphalts not foam at temperatures up to 347°F (175°C). Asphalt cement, if heated to a high enough temperature, will release fumes which will flash in the presence of a spark or open flame. The temperature at which this occurs is called the flashpoint, and is well above temperatures normally used in paving operations. Because of the possibility of asphalt foaming and to ensure an adequate margin of safety, the flashpoint of the asphalt is measured and controlled.
Another important engineering property of asphalt cement is its ductility, which is a measure of a material’s ability to be pulled, drawn, or deformed. In asphalt cements, the presence or absence of ductility is usually more important than the actual degree of ductility because some asphalt cements with a high degree of ductility are also more temperature sensitive. Ductility is measured by an “extension” test, whereby a standard asphalt cement briquette molded under standard conditions and dimensions is pulled at a standard temperature (normally 77°F [25°C]) until it breaks under tension. The elongation at which the asphalt cement sample breaks is a measure of the ductility of the sample.
Environmental protection laws have developed stringent codes limiting water flows and particulate and smoke emissions from oil refineries and asphalt processing plants. Not only dust but sulphur dioxides, smoke, and many other emissions must be rigorously controlled. Electrostatic precipitators, primary dust collectors using single or multiple cone cyclones, and secondary collection units consisting of fabric filter collectors commonly called “baghouses” are all required equipment to control emissions. Hydrocarbons formed in asphalt production, if unchecked, create odoriferous fumes and pollutants, which will stain and darken the air. Pollutants emitted from asphalt production are controlled by enclosures, which capture the exhaust and then recirculate it through the heating process. This not only eliminates the pollution but also increases the heating efficiency of the process.
Higher costs of asphalt cement, stone, and sand have forced the industry to increase efficiencies and recycle old asphalt pavements. In asphalt pavement recycling, materials reclaimed from old pavements are reprocessed along with new materials. The three major categories of asphalt recycling are 1) hot-mix recycling, where reclaimed materials are combined with new materials in a central plant to produce hot-mix paving mixtures, 2) cold-mix recycling, where reclaimed materials are combined with new materials either onsite or at a central plant to produce cold-mix base materials, and 3) surface recycling, a process in which the old asphalt surface pavement is heated in place, scraped down or “scarified,” remixed, relaid, and rolled. Organic asphalt recycling agents may also be added to help restore the aged asphalt to desired specifications.
Because of solvent evaporation and volatility, use of cutback asphalts, especially rapidcure cutback asphalts which use gasoline or naphtha, is becoming more restricted or prohibited while emulsified asphalts (in which only the water evaporates) are becoming more popular because of cost and environmental regulations.
Increasing economic and environmental needs will bring many new technical frefinements to recycling old asphalt pavements, such as using microwaves to completely break down the pavement. Microwaves heat the crushed rock in asphalt pavement faster than the surrounding cement, which is then warmed by the radiant heat from the rock. This method prevents the asphalt cement from burning.
Alternative sources of raw material are being researched, such as the production of synthetic asphalt from the liquefaction of sewage sludge. To ensure consistent product quality, new methods are being developed for manufacturing modified asphalts and emulsions. Many new tests are being developed to help characterize asphalts, such as high-performance gel-permeation chromatography (HP-GPC), which allows many properties to be studied and the results compiled in only a few minutes. New processes, more efficient mixing and milling units, in-line liquid mass flow meters, on-line monitoring systems, and new safety equipment are some other areas being investigated for improvement.
Polymer-modified asphalt crack sealers are gaining in popularity, and many other asphalt modifiers are being developed. Modifiers are added to control pavement rutting, cracking, asphalt oxidation, and water damage. Some commercially available asphalt modifiers are polymers, including elastomers, metal complexes, elemental sulphur, fibres, hydrated lime, Portland cement, silicones, various fillers, and organic anti-strip agents. Many of these modifiers have not been extensively used and are being researched for further development. It might even be possible one day to have “smart asphalt cements” by mixing in certain asphalt friction modifiers which would allow it to change characteristics depending on whether moisture was present. In conjunction with antilock brakes, automatic traction controls, and airbags, this could serve to save many lives on our nation’s highways.
Source – Construction Duniya